1. Field of the Invention
The present invention relates generally to methods and systems for performing venipuncture. More particularly, the present invention relates to a catheter and needle assembly which provides transcutaneous insertion of a large diameter catheter with a smaller diameter needle into a patient's vein with optional blood flashback.
The term “venipuncture” refers generally to the process of obtaining intravenous access for any one of a variety of purposes, including intravenous infusion, therapy, blood sampling, and the like. In the hospital, for example, venipuncture is commonly used to place a small intravenous catheter for delivering intravenous fluids, drug delivery, blood sampling and the like.
Venipuncture for catheter placement comprises placing a catheter over an access needle and inserting the access needle and catheter into a peripheral vein by penetrating the needle through the skin surface. One challenge to venipuncture is the introduction of large diameter catheter. Such introduction frequently requires use of a large diameter needle which can be painful for the patient. While it has been propose to grind down the needle tip to reduce discomfort (see, e.g. U.S. Pat. No. 4,767,407), such grinding significantly increases the cost of the needle. Alternatively, it has been proposed to taper the catheter tip down to the smaller needle diameter (see, e.g. U.S. Pat. No. 6,273,871), but such tapering reduces the catheter tip diameter which can be disadvantageous.
Another challenge to venipuncture is the delay in observing “flashback.” In order to assure that the needle has reached the vein, the person inserting the needle will look for “flashback,” i.e. a flow of blood through a lumen of the needle to a proximal end of the needle where the appearance of blood can be observed. As venous access needles can be long, there can be a perceptible delay between the actual entrance of the needle tip into the vein and the appearance of blood at the proximal end of the needle. While such delays will typically be relatively short, even very small delays between vein entry and the appearance of flashback can result in misplacement of the needle. For example, the needle may continue to be advanced and pierce the opposite wall of the vein. Such “overshoot” is obviously undesirable and should be avoided.
For these reasons, it would be desirable to provide improved apparatus and methods for performing venipuncture. In particular, it would be desirable to provide apparatus and methods which allow the use of reduced size needles for advancing relatively large diameter catheters. It would be further desirable to provide methods and apparatus for detecting blood which minimize the delay between actually entry of a needle tip into a vein and the appearance of blood flashback to the user introducing the needle and catheter. It would be further desirable if such improved methods and apparatus could be provided without the need to significantly modify the design or increase the cost of the catheter and/or access needle and with minimum change in the protocol used by those introducing the needles and catheters. At least some of these objectives will be met by the inventions described below.
2. Description of the Background Art
Needle and catheter assemblies are described in U.S. Pat. Nos. 3,469,579; 4,368,730; 4,767,407; 6,273,871; and U.S. Patent Publ. No. 2011/0208157. The following commonly owned applications, the full disclosures of which are incorporated herein by reference, also describe needle and catheter assemblies: U.S. Patent Publ. Nos. 2010/0094310; 2010/0210934; and 2012/0197200.